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Abstract:

A method for determining the presence of a leak in a pressure system. The
method includes receiving pressure data of the pressure system after
shut-in of the pressure system, determining a pressure slope based on the
pressure data, entering a passing state in response to the slope being
less than a predetermined slope threshold, exiting the passing state in
response to the slope being greater than the predetermined slope
threshold, and generating a passing indication as a result of remaining
in the passing state for at least a predetermined time period.

Claims:

1. A method for determining the presence of a leak in a pressure system,
the method comprising: receiving, by a processor, pressure data of the
pressure system after shut-in of the pressure system; determining, by the
processor, a pressure slope based on the pressure data; entering a
passing state in response to the slope being less than a predetermined
slope threshold; exiting the passing state in response to the slope being
greater than the predetermined slope threshold; and generating a passing
indication as a result of remaining in the passing state for at least a
predetermined time period.

2. The method of claim 1 further comprising generating a failing
indication as a result of the pressure or slope having a value falling
outside a predetermined range.

3. The method of claim 1 wherein the slope is determined over a time
period less than the predetermined time period.

4. The method of claim 1 further comprising pressurizing the pressure
system and upon the pressure system reaching a test pressure shutting in
the pressure system.

5. The method of claim 1 further comprising, after generating a passing
indication, applying a curve-fitting algorithm to the pressure data to
generate a mathematical form that represents the pressure data.

6. The method of claim 1 further comprising exiting the passing state in
response to a change in pressure while in the passing state being greater
than a maximum permitted change in pressure.

7. A method for determining the presence of a leak in a pressure system,
the method comprising: receiving, by a processor, pressure data of the
pressure system after shut-in of the pressure system; determining, by the
processor, a pressure slope based on the pressure data; entering a
passing state in response to the slope being less than a predetermined
slope threshold; exiting the passing state in response to a change in
pressure while in the passing state being greater than a maximum
permitted change in pressure; and generating a passing indication as a
result of remaining in the passing state for at least a predetermined
time period.

8. The method of claim 7 further comprising generating a failing
indication as a result of the pressure or slope having a value falling
outside a predetermined range.

9. The method of claim 7 wherein slope is determined over a time period
less than the predetermined time period.

10. The method of claim 7 further comprising pressurizing the pressure
system and upon the pressure system reaching a test pressure shutting in
the pressure system.

11. The method of claim 7 further comprising, after generating a passing
indication, applying a curve-fitting algorithm to the pressure data to
generate a mathematical form that represents the pressure data.

12. The method of claim 7 further comprising exiting the passing state in
response to the slope being greater than the predetermined slope
threshold.

13. A system for determining the presence of a leak in a pressure system,
the system comprising: at least one pressure sensor coupled to the
pressure system; and a processor coupled to the pressure sensor, the
processor to: receive pressure data from the pressure sensor after
shut-in of the pressure system; determine a pressure slope based on the
pressure data; enter a passing state in response to the slope being less
than a predetermined slope threshold; exit the passing state in response
to the slope being greater than the predetermined slope threshold; and
generate a passing indication as a result of remaining in the passing
state for at least a predetermined time period.

14. The system of claim 13 wherein the processor generates a failing
indication as a result of the pressure or slope having a value falling
outside a predetermined range.

15. The system of claim 13 wherein the slope is determined over a time
period less than the predetermined time period.

16. The system of claim 13 further comprising a pump coupled to the
pressure system via a valve to selectively permit flow between the pump
and the pressure system, the pump to pressurize the pressure system and
the valve to, upon the pressure system reaching a test pressure, shut in
the pressure system.

17. The system of claim 13 wherein after the processor generates a
passing indication, the processor applies a curve-fitting algorithm to
the pressure data to generate a mathematical form that represents the
pressure data.

18. The system of claim 13 wherein the processor further exits the
passing state in response to a change in pressure while in the passing
state being greater than a maximum permitted change in pressure.

19. A system for determining the presence of a leak in a pressure system,
the system comprising: at least one pressure sensor coupled to the
pressure system; and a processor coupled to the pressure sensor, the
processor to: receive pressure data of the pressure system after shut-in
of the pressure system; determine a pressure slope based on the pressure
data; enter a passing state in response to the slope being less than a
predetermined slope threshold; exit the passing state in response to a
change in pressure while in the passing state being greater than a
maximum permitted change in pressure; and generate a passing indication
as a result of remaining in the passing state for at least a
predetermined time period.

20. The system of claim 19 wherein the processor further generates a
failing indication as a result of the pressure or slope having a value
falling outside a predetermined range.

21. The system of claim 19 wherein the slope is determined over a time
period less than the predetermined time period.

22. The system of claim 19 further comprising a pump coupled to the
pressure system via a valve to selectively permit flow between the pump
and the pressure system, the pump to pressurize the pressure system and
the valve to, upon the pressure system reaching a test pressure, shut in
the pressure system.

23. The system of claim 19 wherein after the processor generates a
passing indication, the processor applies a curve-fitting algorithm to
the pressure data to generate a mathematical form that represents the
pressure data.

24. The system of claim 19 wherein the processor further exits the
passing state in response to the slope being greater than the
predetermined slope threshold.

Description:

BACKGROUND

[0001] Tubes, valves, seals, containers, tanks, receivers, pressure
vessels, pipelines, conduits, heat exchangers, and other similar
components, are typically configured to retain and/or transport fluids
under pressure. These components may be referred to as a pressure system.
One example of a pressure system includes a pipeline for transporting
natural gas or other hydrocarbons. Another example is a natural gas well,
an oil well, or other types of wells, whether being actively drilled or
already producing, that typically transports fluids from a producing
geological formation to a well head. Wells may include various
components, such as a Christmas tree, a well head, production tubing,
casing, drill pipe, blowout preventers, completion equipment, coiled
tubing, snubbing equipment, and various other components.

[0002] The fluids retained or transported within pressure systems
typically include one or more gases, liquids, or combinations thereof,
including any solid components entrained within the fluid. A typical
fluid may comprise crude oil, methane or natural gas, carbon dioxide,
hydrogen sulfide, natural gas liquids, water, drilling fluid, and the
like. Other examples include hydraulic fluid within a hydraulic line.

[0003] Many pressure systems are tested to ensure that the pressure system
is not leaking and that the pressure system is capable of maintaining
pressure integrity. However, performing such pressure tests often
requires a test pressure within the pressure system to be held for a
significant period of time until a steady-state test pressure (i.e., one
in which the test pressure changes very little with time) is reached.
That is, it may be only after a steady-state pressure is reached that an
operator might be assured that a decrease in pressure was a result of the
fluid cooling via a transfer of heat from the fluid to the sea and/or
other surrounding media rather than because of a leak. In addition, tests
may be repeated several times to ensure validity of the tests, which
results in even more time spent testing. This testing process is costly
because the tests could take from 12 to 24 hours to complete when, for
example, an offshore drilling vessel or rig leases for $800,000 per day.

SUMMARY

[0004] The problems noted above are solved in large part by a method for
determining the presence of a leak in a pressure system. The method
includes receiving pressure data of the pressure system after shut-in of
the pressure system, determining a pressure slope based on the pressure
data, entering a passing state in response to the slope being less than a
predetermined slope threshold, exiting the passing state in response to
the slope being greater than the predetermined slope threshold, and
generating a passing indication as a result of remaining in the passing
state for at least a predetermined time period.

[0005] The problems noted above may be further solved by another method
for determining the presence of a leak in a pressure system. The method
includes receiving pressure data of the pressure system after shut-in of
the pressure system, determining a pressure slope based on the pressure
data, entering a passing state in response to the slope being less than a
predetermined slope threshold, exiting the passing state in response to a
change in pressure while in the passing state being greater than a
maximum permitted change in pressure, and generating a passing indication
as a result of remaining in the passing state for at least a
predetermined time period.

[0006] The problems noted above may be still further solved by a system
for determining the presence of a leak in a pressure system. The system
includes at least one pressure sensor coupled to the pressure system and
a processor coupled to the pressure sensor. The processor receives
pressure data from the pressure sensor after shut-in of the pressure
system, determines a pressure slope based on the pressure data, enters a
passing state in response to the slope being less than a predetermined
slope threshold, exits the passing state in response to the slope being
greater than the predetermined slope threshold, and generates a passing
indication as a result of remaining in the passing state for at least a
predetermined time period.

[0007] The problems noted above may also be solved by another system for
determining the presence of a leak in a pressure system. The system
includes at least one pressure sensor coupled to the pressure system and
a processor coupled to the pressure sensor. The processor receives
pressure data of the pressure system after shut-in of the pressure
system, determine a pressure slope based on the pressure data, enters a
passing state in response to the slope being less than a predetermined
slope threshold, exits the passing state in response to a change in
pressure while in the passing state being greater than a maximum
permitted change in pressure, and generates a passing indication as a
result of remaining in the passing state for at least a predetermined
time period.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a detailed description of exemplary embodiments of the
disclosure, reference will now be made to the accompanying drawings in
which:

[0009] FIG. 1 shows a block diagram of a leak detection system in
accordance with various embodiments;

[0010] FIG. 2 shows an exemplary leak detection system used to test a
blowout preventer on an oil rig in accordance with various embodiments;

[0011] FIG. 3 shows a flow chart and state diagram of a method for
determining the presence of a leak in a pressure system in accordance
with various embodiments;

[0012] FIG. 4 shows another flow chart and state diagram of a method for
determining the presence of a leak in a pressure system in accordance
with various embodiments;

[0013] FIG. 5 shows another flow chart and state diagram of a method for
determining the presence of a leak in a pressure system in accordance
with various embodiments; and

[0014] FIG. 6 shows another flow chart and state diagram of a method for
determining the presence of a leak in a pressure system in accordance
with various embodiments.

NOTATION AND NOMENCLATURE

[0015] Certain terms are used throughout the following description and
claims to refer to particular system components. As one skilled in the
art will appreciate, companies may refer to a component by different
names. This document does not intend to distinguish between components
that differ in name but not function. In the following discussion and in
the claims, the terms "including" and "comprising" are used in an
open-ended fashion, and thus should be interpreted to mean "including,
but not limited to . . . ." Also, the term "couple" or "couples" is
intended to mean either an indirect or direct connection. When used in a
mechanical context, if a first component couples or is coupled to a
second component, the connection between the components may be through a
direct engagement of the two components, or through an indirect
connection that is accomplished via other intermediate components,
devices and/or connections. In addition, when used in an electrical
context, if a first device couples to a second device, that connection
may be through a direct electrical connection, or through an indirect
electrical connection via other devices and connections.

[0016] As used herein, the term "state"--as in "passing state" or "failing
state"--refers to the state of a computing device when a particular
constraint is satisfied. For example, a computing device may be in a
passing state when passing constraints are met and may be in a failing
state when failing constraints are met. Further, being in a passing state
does not necessarily indicate that a test has been passed and being in a
failing state does not necessarily indicate that a test has been failed;
in some cases, additional constraints must be satisfied in the passing
state for the test to be passed and additional constraints must be
satisfied in the failing state for the test to be failed.

[0017] As used herein, the terms "rate of change," "slope," and "first
derivative" all refer to the same characteristic of a value.

[0018] As used herein, the terms "curvature" and "second derivative" all
refer to the same characteristic of a value.

DETAILED DESCRIPTION

[0019] The following discussion is directed to various embodiments of the
disclosure. Although one or more of these embodiments may be preferred,
the embodiments disclosed should not be interpreted, or otherwise used,
as limiting the scope of the disclosure, including the claims. In
addition, one skilled in the art will understand that the following
description has broad application, and the discussion of any embodiment
is meant only to be exemplary of that embodiment, and not intended to
intimate that the scope of the disclosure, including the claims, is
limited to that embodiment.

[0020] FIG. 1 shows a block diagram of a leak detection system 1 in
accordance with various embodiments of the present disclosure. The leak
detection system 1 includes a pressure system 5. The pressure system may
include various tubes, valves, seals, containers, vessels, heat
exchangers, pumps, pipelines, conduits, and other similar components to
retain and/or transport fluids through the pressure system 5. As
explained above, examples of the pressure system 5 include a pipeline for
transporting natural gas or other hydrocarbons or other fluids, blow-out
preventers, various wells including casing and other completion
components, hydraulic or fuel lines, fluid storage containers, and other
types of systems for transporting or retaining fluids.

[0021] The pressure system 5 may contain fluids such as gases, liquids, or
combinations thereof, including any solid components entrained within the
fluid. Examples of fluids include crude oil, methane, natural gas, carbon
dioxide, hydrogen sulfide, natural gas liquids, and the like. Where the
pressure system 5 comprises an exploration oil or gas well, the fluids
typically include drilling fluids, lost circulation materials, various
solids, drilled formation solids, and formation fluids and gases.

[0022] The leak detection system 1 may include a fluid pumping unit 10,
which may be a cementing unit or a pump. The fluid pumping unit 10 is
coupled to the pressure system 5. The fluid pumping unit 10 supplies a
selected or particular volume of a test fluid from a source or reservoir
of fluid to the pressure system 5. The selected or particular volume may
be based on a desired pressure for the pressure system 5; that is, the
volume supplied may be chosen such that the pressure system 5 reaches a
desired pressure. The test fluid may comprise water, water with
additional additives, drilling fluid, completion fluid or a fluid of the
type already present in the pressure system 5, or other combinations
thereof. The selected volume of test fluid depends, in part, on the size
or total volume of the pressure system 5, and can be from small amounts,
such as microliters for laboratory equipment, to large amounts, such as
barrels and more, for large pressure systems, such as pipelines and oil
and gas wells. Adding test fluid to the pressure system 5 raises the
pressure at which the fluid within the pressure system 5 is confirmed,
such that a test pressure is reached that is greater than the initial
pressure of the fluid in the pressure system 5. The pressure system 5 may
be shut-in once the pressure system 5 reaches a desired test pressure.

[0023] Optionally, a flow meter 30 is coupled to the fluid pumping unit 10
to sense the amount of fluid being added to the pressure system 5. The
flow meter 30 may comprise a venturi flow meter, a pressure flow meter, a
stroke counter, an impeller flow meter, or other similar flow meters. The
flow meter 30 optionally displays a signal that indicates the flow of the
fluid, such as a flow rate, via gauges and/or digital displays. The flow
meter 30 optionally transmits a signal reflective of the flow rate to a
processor 15, for example via sensor cables or wirelessly (e.g., via
Internet 27 or another wireless network).

[0024] The leak detection system 1 also includes at least one pressure
sensor 20 coupled to the pressure system 5. The pressure sensor 20 senses
a pressure of the fluid within the pressure system 5 before, during, and
after pressurization of the pressure system 5. In some embodiments, the
pressure sensor 20 displays a signal that indicates the pressure of the
fluid within the pressure system 5, for example via gauges and/or digital
displays. The pressure sensor 20 transmits a signal that indicates the
pressure to the processor 15, typically via sensor cables, although it is
contemplated that the pressure sensor 20 can be configured to transmit
the signal wirelessly. The pressure sensor 20 may be selected for the
particular operating conditions, such as a pressure and temperature range
that is expected for the fluid within the pressure system 5. For example,
a pressure sensor 20 selected for use in a pressure system that is part
of an oil well, such as a blowout preventer, would be capable of sensing
a wide range of pressures at a wide range of temperatures.

[0025] The processor 15 may be a component in a variety of computers such
as laptop computers, desktop computers, netbook and tablet computers,
personal digital assistants, smartphones, and other similar devices and
can be located at the testing site or remote from the site. One skilled
in the art will appreciate that these computing devices include other
elements in addition to the processor 15, such as display device 25,
various types of storage, communication hardware, and the like. The
processor 15 may be configured to execute particular software programs to
aid in the testing of a pressure system 5. The functionality of these
programs will be described in further detail below.

[0026] As noted above, the processor 15 may couple to a display device 25,
in some cases by way of intermediate hardware such as a graphics
processing unit or video card. The display device 25 includes devices
such as a computer monitor, a television, a smartphone display, or other
known display devices.

[0027] In connection with fluids and gases that exhibit a potentially
significant change in pressure as a function of the fluid's temperature,
it can be difficult to determine whether a change in pressure in a
pressure system is merely a result of the change in temperature of the
fluid, or if it is a result of a leak somewhere within the pressure
system. For example, a fixed volume of a synthetic drilling fluid in a
suitable container/pressure vessel used in oil and gas drilling exhibits
a decreasing pressure as a function of decreasing temperature. Depending
on the drilling fluid involved, the pressure can very significantly with
temperature. In deep water offshore drilling, the drilling fluid may be
at a particular temperature at the surface before being pressurized. As
the pressure system is pressurized with drilling fluid, the temperature
of the drilling fluid rises as a result of its increase in pressure, and
thus may exceed the ambient temperature of the fluid when it was at the
surface.

[0028] The fluid is subsequently cooled as it resides in a wellhead or
blow-out preventer that can be several thousand feet below the surface of
the ocean and on the sea floor where the ambient water temperature may be
as low as 34° F. Thus, there is a large and rapid transfer of heat
energy from the drilling fluid, through the containing drill pipe and/or
riser, to the surrounding ocean, which, in turn, causes a sometimes
significant decrease in the pressure of the fluid held within the
pressure system. In accordance with various embodiments of the present
disclosure, a system and method for analyzing pressure response of the
pressure system to determine the presence of a leak in the pressure
system distinguishes a drop in pressure caused by the decrease in
temperature from a drop in pressure caused by a leak within the pressure
system.

[0029] It is contemplated that the test pressure data acquired and stored
in the computer readable medium optionally undergoes some form of data
smoothing or normalizing processes to eliminate spikes or data
transients. For example, one may use procedures to perform a moving
average, curve fitting, and other such data smoothing techniques.

[0030] FIG. 2 shows an exemplary embodiment of the leak detection system
in the context of a deepwater exploration well in which the blowout
preventer and, more specifically, various subcomponents of the blowout
preventer that can be hydraulically isolated from the other components,
are tested for leaks and pressure integrity. The leak detection system of
FIG. 2 is associated with a pressure system 5A that includes, in this
example, flow line 4A (which may be one or more flow lines) that couple a
fluid pumping unit 10A, typically a cementing unit when on a drilling
rig, to one or more annular blowout preventers 6A and one or more shear
rams and/or pipe rams 7A. Additionally, FIG. 2 also illustrates the
casing 8A, open well bore 9A, and the formation or geological
structure/rock 11A that surrounds the open well bore 9A. The various
embodiments of the present disclosure extend to all such elements for
leak detection and pressure integrity testing.

[0031] Also illustrated in FIG. 2 is a flow meter or flow sensor 30A
coupled to a processor 15A as previously described. Also illustrated are
two pressure sensors 20A and 20B coupled to the pressure system 5A, one
at the surface and one at the blowout preventer. In certain embodiments,
other pressure sensors may be located at the same or different locations
of the pressure system 5A. The pressure sensors 20A and 20B shown are
coupled to the processor 15A as described above. A display device 25A,
comparable to that described above, is also coupled to the processor 15A.

[0032] A further application and benefit of the disclosed methods and
systems accrue in the particular scenario in which a low pressure test
precedes a high pressure test. The ability to detect a leak during the
low pressure test, something difficult given the resolution and
capability of prior art methods, for example using a circular chart
recorder, permits a user of the present disclosure to take remedial
action to investigate and/or to stop a leak following a the low pressure
test and before preceding to the high pressure test phase. Taking
preventive or remedial action at the low pressure test phase reduces risk
to equipment that might fail catastrophically under high pressures;
reduces risk to personnel that might otherwise be in the area of the
equipment or pressure systems during which the pressure systems fail
while they undergo a high pressure test; reduces the risk to the
environment should the pressure systems otherwise fail while they undergo
a high pressure test; and reduces the time to detect the leak because a
leak could potentially be discovered at the low pressure stage before
undertaking the time and money to conduct a high pressure test.

[0033] Turning now to FIG. 3, a method 300 for determining the presence of
a leak in a pressure system 5 is shown in accordance with various
embodiments. The method 300 begins in block 302, where the pressure
system 5 may be pressurized, for example by a pump device. Upon a shut-in
event 304, the method proceeds to block 305 to wait for a buffer time
period before beginning analysis of the pressure system 5. In some
embodiments, the buffer period enables a pre-determined amount of data
(e.g., to perform a first determination of a pressure rate of change) to
be obtained. When the buffer time period is complete, the method 300
continues to determining a slope of pressure data, which is based on
pressure data received by the processor 15 (e.g., from the pressure
sensor 20). In accordance with various embodiments, if the pressure slope
is greater than a predetermined threshold, the method 300 continues to
determine the pressure slope in block 306. In some cases, the
predetermined threshold is a value determined through practical
application such that a slope in excess of the threshold is likely to
indicate that the pressure system 5 is still responding, in large part,
to the change in temperature of the fluid in the pressure system 5.
Similarly, a slope below the threshold is likely to indicate that the
pressure system 5 is no longer responding, for the most part, to the
change in temperature of the fluid in the pressure system 5.

[0034] When the slope is below the predetermined threshold, the method 300
enters a passing state in block 308 and continues to determine the
pressure slope, remaining in the passing state provided that the slope is
below the predetermined threshold. If the slope exceeds the predetermined
threshold in block 308, the method 300 continues with exiting the passing
state and returning to block 306 where the slope is again determined to
identify whether it drops below the predetermined threshold, which causes
the method 300 to return to the passing state block 308.

[0035] However, if the pressure slope remains below the predetermined
threshold in block 308 for at least a predetermined time period (e.g., 5
minutes), the method 300 continues to block 310 where a passing
indication is generated, for example for display on the display device 25
or for transmittal via a network such as Internet 27 to another computing
device 28 or another display device.

[0036] In some embodiments, the method 300 also includes generating a
failing indication in block 312 if pressure data received from the
pressure sensor 20 indicates that the pressure value has fallen out of a
predetermined range (e.g., the pressure of the pressure system 5 is below
a minimum pressure value). Alternately, the method 300 may include
generating a failing indication in block 312 if the slope of the pressure
data received from the pressure sensor 20 indicates that the slope is
outside of a predetermined range.

[0037] In accordance with various embodiments, the slope of the pressure
data received from the pressure sensor 20 may be determined (e.g., by the
processor 15) over a time period less than the predetermined time period
for generating a passing indication. For example, although the time
period for generating a passing indication may be 5 minutes, the slope
may be determined over a one-minute time period, a 30-second time period,
or time period of less than one second. As explained above, noise (e.g.,
environmental noise) may be introduced to the pressure data from the
pressure sensor 20. In certain embodiments, the pressure data may thus
undergo data smoothing or normalizing processes to eliminate noise, such
as spikes or data transients. For example, a moving average, curve
fitting, and other such data smoothing techniques may be applied to the
pressure data prior to determining a slope of the pressure data.

[0038] Turning now to FIG. 4, a method 400 for determining the presence of
a leak in a pressure system 5 is shown in accordance with various
embodiments. The method 400 begins in block 402, where the pressure
system 5 may be pressurized, for example by a pump device. Upon a shut-in
event 304, the method proceeds to block 305 to wait for a buffer time
period before beginning analysis of the pressure system 5. The buffer
period may serve as an initial data-gathering period as explained above.
When the buffer time period is complete, the method 400 continues to
determining a slope of pressure data, which is based on pressure data
received by the processor 15 (e.g., from the pressure sensor 20). In
accordance with various embodiments, if the pressure slope is greater
than a predetermined threshold, the method 400 continues to determine the
slope in block 406. In some cases, the predetermined threshold is a value
determined through practical application such that a slope in excess of
the threshold is likely to indicate that the pressure system 5 is still
responding, in large part, to the change in temperature of the fluid in
the pressure system 5. Similarly, a slope below the threshold is likely
to indicate that the pressure system 5 is no longer responding, for the
most part, to the change in temperature of the fluid in the pressure
system 5.

[0039] When the slope is below the predetermined threshold, the method 400
enters a passing state in block 408 and begins to monitor the absolute
pressure change from the time the passing state is entered. The method
400 remains in the passing state (block 408) provided that the absolute
pressure change remains below a maximum permitted change in pressure. If
the absolute pressure change from the time the passing state is entered
exceeds the maximum permitted change in block 408, the method 400
continues with exiting the passing state and returning to block 406 where
the slope is determined to identify whether it drops below the
predetermined threshold, which causes the method 400 to return to the
passing state block 408.

[0040] However, if the absolute pressure change remains below the maximum
permitted change in pressure in block 408 for at least a predetermined
time period (e.g., 5 minutes), the method 400 continues to block 410
where a passing indication is generated, for example for display on the
display device 25 or for transmittal via a network such as Internet 27 to
another computing device 28.

[0041] In some embodiments, the method 400 also includes generating a
failing indication in block 412 if pressure data received from the
pressure sensor 20 indicates that the pressure value has fallen out of a
predetermined range (e.g., the pressure of the pressure system 5 is below
a minimum pressure value). Alternately, the method 400 may include
generating a failing indication in block 412 if the slope of the pressure
data received from the pressure sensor 20 indicates that the slope is
outside of a predetermined range.

[0042] As above, the slope of the pressure data received from the pressure
sensor 20 may be determined (e.g., by the processor 15) over a time
period less than the predetermined time period for generating a passing
indication. For example, although the time period for generating a
passing indication may be 5 minutes, the slope may be determined over a
one-minute time period, a 30-second time period, or time period of less
than one second. As explained above, noise (e.g., environmental noise)
may be introduced to the pressure data from the pressure sensor 20. In
certain embodiments, the pressure data may thus undergo data smoothing or
normalizing processes to eliminate noise, such as spikes or data
transients. For example, a moving average, curve fitting, and other such
data smoothing techniques may be applied to the pressure data prior to
determining a rate of change.

[0043] FIG. 5 shows a method 500 for determining the presence of a leak in
a pressure system 5, which combines aspects of FIGS. 3 and 4. The method
500 is similar to methods 300 and 400 in blocks 502-506. Further, the
method 500 also enters the passing state in block 508 in response to the
slope being below a predetermined threshold. In the passing state (blocks
508 and 510), both the pressure slope and the absolute pressure change
from the time the passing state is entered are monitored. The method 500
remains in the passing state provided that the slope is below the
predetermined threshold, a threshold that may in some embodiments change
over time to narrow the allowable slope as time passes, and that the
absolute pressure change is below a maximum permitted change in pressure.
If either the slope exceeds the predetermined threshold (in block 510) or
the absolute pressure change from the time the passing state is entered
exceeds the maximum permitted change in pressure (in block 508), the
method 500 exits the passing state and returns to block 506. While in
block 506, if the slope drops below the predetermined threshold, the
method 500 returns to the passing state of blocks 508 and 510.

[0044] However, if the slope remains below the predetermined threshold in
block 510 and the absolute pressure change from the time the passing
state is entered remains below the maximum permitted change in pressure
in block 508 for at least a predetermined time period (e.g., 5 minutes),
the method 500 continues to block 512 where a passing indication is
generated, for example for display on the display device 25 or for
transmittal via a network such as Internet 27 to another computing device
28.

[0045] In some embodiments, the method 500 also includes generating a
failing indication in block 514 if pressure data received from the
pressure sensor 20 indicates that the pressure value has fallen out of a
predetermined range (e.g., the pressure of the pressure system 5 is below
a minimum pressure value). Alternately, the method 500 may include
generating a failing indication in block 514 if the slope of the pressure
data received from the pressure sensor 20 indicates that the slope is
outside of a predetermined range.

[0046] FIG. 6 shows a method 600 for determining the presence of a leak in
a pressure system 5 in accordance with various embodiments. The method
600 is similar to methods 300, 400, and 500 in blocks 602-605. When the
buffer time period is complete in block 605, the method 600 continues to
block 606 and determining a slope of pressure data as well as determining
a curvature of the pressure data (i.e., a second derivative of pressure
data or a derivative of the slope), both of which are based on pressure
data received by the processor 15 (e.g., from the pressure sensor 20).

[0047] In accordance with various embodiments, if the pressure slope is
above a predetermined threshold and the curvature indicates a declining
slope, the method 600 continues to determine the pressure slope and
curvature in block 606. If the curvature indicates an absolute value of
the slope is decreasing, it is likely that the pressure slope is
improving and will eventually fall below the predetermined threshold and
further analysis may result in a passing test. On the other hand, if the
curvature indicates an absolute value of the slope is constant or
increasing, it is likely that the slope is not significantly improving
and a the current slope indicates the presence of a leak. In some cases,
rather than comparing the curvature to indications of increasing,
constant, or decreasing slope, the curvature may be compared to a
predetermined threshold, which is a value determined through practical
application such that a curvature in excess of the threshold is likely to
indicate that the pressure slope is not significantly improving and the
current slope indicates a leak. Similarly, a curvature below the
threshold is likely to indicate that the slope, while not below the
predetermined maximum passing value, is improving and further analysis
may result in a passing test. If the slope is not below the predetermined
threshold, the method 600 remains in block 606. Additionally, if the
curvature indicates a constant or increasing slope, the method 600 may
continue to block 612 with generating a failing indication or an
indication that test failure is likely or imminent.

[0048] When the slope is below a predetermined threshold, the method 600
enters a passing state in block 608 and continues to determine the slope,
remaining in the passing state provided that the slope is below the
predetermined threshold. If the slope exceeds the predetermined threshold
in block 608, the method 600 continues with exiting the passing state and
returning to block 606 where the curvature and slope are again determined
to identify whether the slope drops below the predetermined threshold,
which causes the method 600 to return to the passing state in block 608,
or whether the curvature indicates that the slope is not improving.
However, as above, if the slope remains below the predetermined threshold
in block 608 for at least a predetermined time period (e.g., 5 minutes),
the method 600 continues to block 610 where a passing indication is
generated, for example for display on the display device 25 or for
transmittal via a network such as Internet 27 to another computing device
28. Additionally, although not illustrated for brevity, the method 600
may transition to the passing state as shown in FIGS. 4 and 5 as well.

[0049] In accordance with various embodiments, the slope and curvature of
the pressure data received from the pressure sensor 20 may be determined
(e.g., by the processor 15) over a time period less than the
predetermined time period for generating a passing indication. For
example, although the time period for generating a passing indication may
be 5 minutes, the slope and curvature may be determined over a one-minute
time period, a 30-second time period, or time period of less than one
second. As explained above, noise (e.g., environmental noise) may be
introduced to the pressure data from the pressure sensor 20. In certain
embodiments, the pressure data may thus undergo data smoothing or
normalizing processes to eliminate noise, such as spikes or data
transients. For example, a moving average, curve fitting, and other such
data smoothing techniques may be applied to the pressure data prior to
determining the slope or curvature.

[0050] In certain embodiments, after generating either a passing
indication, a curve-fitting algorithm may be applied to the pressure
data. This application may utilize a variety of curve fitting approaches,
such as least squares, and a variety of curve types, such as polynomials,
exponential, ellipses including combinations of curves to best arrive at
a mathematical form, such as a formula or equation, that describes
pressure data change and value over time. Statistical values for
"goodness of fit," such as standard deviations and "R-squared," may be
utilized to determine if a function or equation adequately describes the
pressure data in a mathematical form. In accordance with various
embodiments, the mathematical form may be used as a replacement for raw
data as a benchmark for comparative tests and is beneficial because
smoothed data can provide a boost in computational efficiency without
compromising accuracy when compared to methods and system using raw data
as a benchmark.

[0051] Referring briefly back to FIG. 1, the processor 15 is configured to
execute instructions read from a computer readable medium, and may be a
general-purpose processor, digital signal processor, microcontroller,
etc. Processor architectures generally include execution units (e.g.,
fixed point, floating point, integer, etc.), storage (e.g., registers,
memory, etc.), instruction decoding, peripherals (e.g., interrupt
controllers, timers, direct memory access controllers, etc.),
input/output systems (e.g., serial ports, parallel ports, etc.) and
various other components and sub-systems. The program/data storage 35 is
a computer-readable medium coupled to and accessible to the processor 15.
The storage 35 may include volatile and/or non-volatile semiconductor
memory (e.g., flash memory or static or dynamic random access memory), or
other appropriate storage media now known or later developed. Various
programs executable by the processor 15, and data structures
manipulatable by the processor 15 may be stored in the storage 30. In
accordance with various embodiment, the program(s) stored in the storage
30, when executed by the processor 15, may cause the processor 15 to
carry out any of the methods described herein.

[0052] The above discussion is meant to be illustrative of the principles
and various embodiments of the present disclosure. Numerous variations
and modifications will become apparent to those skilled in the art once
the above disclosure is fully appreciated. For example, while the
embodiments are discussed relating to pressure data from a blowout
preventer on a drilling rig, it is understood that embodiments of the
presently disclosed system and method of detecting leaks may be applied
to pressure systems and fluid systems of other types, as disclosed and
discussed above. It is intended that the following claims be interpreted
to embrace all such variations and modifications.